Field of Invention
The invention relates to an optical device and, in particular, to an autostereoscopic projection device.
Related Art
Recently, with the progress of the stereoscopic display technology, many stereoscopic products, such as stereoscopic movies and stereoscopic TVs, are produced for various commercial applications. The basic concept of the stereoscopic display technology is to transmit the left-eye images and the right-eye images with different viewing angles to the left eye and right eye of the viewer respectively, and both of these 2D images are then combined in the viewer's brain to give the perception of 3D depth while the viewer perceive the stereoscopic images.
The stereoscopic display technology can be divided into the glasses type, head-mounted type and autostereoscopic type according to the applied tools. Especially, the autostereoscopic display technology attracts more attention from industries because it needn't stereoscopic glasses or head-mounted devices but can provide 3D images to the naked eyes of the viewers.
A conventional autostereoscopic projection device cooperates with a plurality of projection apparatuses (may be disposed in an array) so that the left eye and the right eye can view different images. However, this kind of design causes a considerable difficulty to the compactness of the projection device, and the optical path design among the projection apparatuses will become more complicated. Another design for achieving the same purpose is to transmit the images of different angles to the left eye and right eye respectively at different timings by the liquid crystal (LC) switch elements. Although such design can reduce the volume of the projection device, more LC switch elements need to be used for the more viewing angles. For example, if 16 viewing angles are provided, four stages of two-phase LC switches are needed. Because the conversion efficiency ratio of each of the two-phase LC switches is about 90%, the actual total conversion efficiency ratio drops off to about 65.6% after the four-time LC switching. Accordingly, this design of using the switch elements not only complicates the control but also reduces the total imaging efficiency.
Therefore, it is an important subject to provide an autostereoscopic projection device which has simpler optical path design, simpler control mechanism, better conversion efficiency, and less volume and weight.